Devices, systems, and methods for measuring differential temperature

ABSTRACT

At least one exemplary embodiment of the present invention includes a method comprising providing an input signal from a first differential temperature sensor to a first primary coil of a transformer, and detecting a transient signal from a secondary coil of the transformer, said transient signal arising upon a halting of the input signal. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. This abstract is submitted with the understanding that it will not be used to interpret or limit the scope.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and incorporates byreference in its entirety, U.S. Provisional Patent Application SerialNo. 60/336,590, filed Dec. 5, 2001, titled “System for Measurement ofTemperature Differentials and Minute Current Flow”.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The wide variety of potential embodiments of the presentinvention will be more readily understood through the following detaileddescription, with reference to the accompanying drawings in which:

[0003]FIG. 1 is a circuit diagram of an exemplary embodiment of a system1000 of the present invention.

[0004]FIG. 2 is a block diagram of an exemplary embodiment of aninformation device 2000 of the present invention.

[0005]FIG. 3 is a block diagram of an exemplary embodiment of adifferential thermocouple 3000 of the present invention.

[0006]FIG. 4 is a flow diagram of an exemplary embodiment of a method4000 of the present invention.

[0007]FIG. 5 is a flow diagram of an exemplary embodiment of a method5000 of the present invention.

[0008]FIG. 6 is a circuit diagram of an exemplary embodiment of a system6000 of the present invention.

[0009]FIG. 7 is a circuit diagram of an exemplary embodiment of a system7000 of the present invention.

[0010]FIG. 8 is a set of inter-linked timing diagrams of an exemplaryembodiment of a method 8000 of the present invention.

DETAILED DESCRIPTION

[0011] Certain embodiments of the present invention provide a methodcomprising providing an input signal from a first differentialtemperature sensor to a first primary coil of a transformer, anddetecting a transient signal from a secondary coil of the transformer,said transient signal arising upon a halting of the input signal.

[0012] Certain embodiments of the present invention provide a methodcomprising detecting a transient signal from a secondary coil of atransformer, the transient signal arising upon an interruption of aninput signal from a current-producing transducer provided to a firstprimary coil of the transformer; and providing a current to the secondprimary coil of the transformer to cause an energy present in thetransient signal to equal a reference energy present in a referencetransient signal produced by the secondary coil of the transformer whenno temperature differential is sensed by the current-producingtransducer.

[0013] Certain embodiments of the present invention provide a systemcomprising a first differential thermocouple sensor electrically coupledto a first modulator having a duty cycle, an output of said firstmodulator electrically coupled to a first primary coil of a transformer,and a second differential thermocouple sensor electrically coupled to asecond modulator having a duty cycle, said second modulator electricallycoupled to a second primary coil of said transformer, said first primarycoil balanced with said second primary coil, a secondary coil of saidtransformer electrically coupled to said first a processor adapted todetect a transient output of said secondary coil of said transformer andfilter a steady-state output of said secondary coil of said transformer.

[0014]FIG. 1 is a circuit diagram of an exemplary embodiment of a system1000 of the present invention. System 1000 can include a firstdifferential thermocouple 1110 that can be electrically coupled to afirst primary coil 1120 of a transformer 1010. First differentialthermocouple 1110 can also be connected via a first controllable switch1130, such as a field effect transistor (FET), and a resistor 1140 toground.

[0015] System 1000 also can include a second differential thermocouple1210 that can be electrically coupled to a second primary coil 1220 oftransformer 1010. Second differential thermocouple 1210 can also beconnected via a second controllable switch 1230, such as a field effecttransistor (FET), and a resistor 1240 to ground. A balancing currentdevice 1270 can provide, via a resistor 1280, a current signal of apredetermined form, duration, amplitude, and/or direction through seconddifferential thermocouple 1210.

[0016] The inputs of first and second primary coils can be balanced interms of resistance, capacitance, and/or temperature coefficients. Anyof resistors 1140 and/or 1240 can be of relatively low resistance, e.g.less than one ohm, and can have a very low temperature coefficient. Anyresistor used in any embodiment, such as for example resistors 1140and/or 1240, can be fabricated from a material having a very lowtemperature coefficient, such as for example, Mangininand/or Even Ohm.

[0017] In certain embodiments, controllable switches 1130 and/or 1230can have a nearly infinite resistance in the “off” state and a nearlyzero resistance in the “on” state. Certain FET's, such as the PhillipsSemiconductor IRFZ44N and/or the International Rectifier IRL1404, whichhave an “on” state resistance of 22 milli-Ohms and 4 milli-Ohms,respectively. The state change time and/or slew rate can be on the orderof approximately 10 to approximately 100 nanoseconds, including everyvalue therebetween.

[0018] Any resistor of any embodiment (e.g., 1140, 1240, and/or 1211(shown in FIGS. 6 and 7), switches 1130, 1230, and/or transformer 1010can be thermally stabilized prior to and/or during use.

[0019] Transformer 1010 can also include a secondary coil 1320, whichcan be coupled via a grounded resistor 1330 to one or more amplifiers1340. An amplified output of secondary coil 1320 can be provided to aA/D converter 1350, and then to a information device 1370. The analogand/or digital output of secondary coil 1320 can also be provided to anoscilloscope and/or spectrum analyzer 1360. Electrically coupled toinformation device 1370 can be an output device 1390. Information device1370 can include and/or be coupled to a timing device 1380 that cantrigger the opening and closing of switches 1130 and/or 1230.Information device 1370 can be coupled to current device 1270.

[0020] When switch 1130 opens its circuit, the magnetic field withintransformer 1010 can collapse, permitting current flow and a transfer ofenergy from primary coil 1120 to secondary coil 1320 of transformer1010. Likewise, when switch 1230 opens its circuit, the magnetic fieldwithin transformer 1010 can collapse, permitting current flow and atransfer of energy from primary coil 1220 to secondary coil 1320 oftransformer 1010. The energy flow through secondary coil 1320 cancomprise a transient output signal in the form of a signal pulse havinga time dependent decay. The period of decay can be controlled byadjusting swamping resistor 1330 and/or other well-known circuitparameters.

[0021] As a result of a temperature differential between thermocouplejunctions 1114, 1212, and 1214 in a uniform temperature zone 1118, andtemperature at thermocouple junction 1112, an EMF will be generated andcurrent will flow from the first differential thermocouple 1110 to firstprimary coil 1120 when switch 1130 is in a conductive state. Via currentdevice 1150, information device 1370 can input current to the second orbalancing primary coil 1220 such that a null output is produced at thesecondary coil 1220. The amount of current necessary to produce the nulloutput can be measured at current device 1150 and/or information device1370 and employed to compute an output temperature differential signalwhich can be provided to an output device 1390, such as a monitor,display, printer, annunciator, speaker, and/or pager.

[0022] In practice, system 1000 can be first set to a null state, i.e.having no EMF or current flow through the secondary coil 1320. Intheory, no current will flow through secondary coil 1320 if allthermocouple junctions, 1112, 1114, 1212, and 1214 are at the sametemperature, i.e. there is no temperature differential.

[0023] Due to Nyquist noise, Johnson noise, parasitic voltages,capacitance, thermal junction EMF and other factors, a minute current isgenerated even when all of the thermocouple junctions are at the sametemperature.

[0024] In order to set the system to a null state, all of thethermocouple junctions can be set the same temperature and thereafter, acurrent can be applied to the balancing coil 1220 to adjust the outputsignal from the secondary coil 1320 to zero. Such nulling current(I_(x)) can be measured at the balancing current device 1250 and can beestablished as the null current level for the system.

[0025] The system can utilize the difference between the establishednull current level (I_(x)) (with all thermocouple junctions at the sametemperature) and the current level (I_(y)) necessary to balance thesystem with a temperature differential between the junctions 1112, 1114for the purpose of calculating the value of the temperaturedifferential.

[0026] The difference (I_(d)) between the null current level and thebalancing current level necessary to obtain a zero secondary coil outputat the temperature difference, i.e. I_(x)−I_(y) can be proportional tothe degree of temperature difference between the thermocouple junctions1112, 1114.

[0027] Utilizing device 1000, a temperature difference can be sensed towithin approximately 0.005K, approximately 0.001K, approximately0.0005K, and/or approximately 0.0001K, including every valuetherebetween.

[0028]FIG. 2 is a block diagram of an exemplary embodiment of aninformation device 2000 of the present invention. Information device2000 can represent information device 1370 of FIG. 1.

[0029] Information device 2000 can be implemented as a spectrumanalyzer, on a general purpose or special purpose computer, such as apersonal computer, workstation, minicomputer, mainframe, supercomputer,laptop, and/or Personal Digital Assistant (PDA), etc., a programmedmicroprocessor or microcontroller and/or peripheral integrated circuitelements, an ASIC or other integrated circuit, a hardware electroniclogic circuit such as a discrete element circuit, and/or a programmablelogic device such as a PLD, PLA, FPGA, or PAL, or the like, etc. Ingeneral any device on which resides a finite state machine capable ofimplementing the at least a portion of a method described herein may beused.

[0030] Information device 2000 can include well-known components such asone or more communication interfaces 2100, one or more processors 2200,one or more memories 2300 containing instructions 2400, and/or one ormore input/output (I/O) devices 2500, etc.

[0031] In one embodiment, communication interface 2100 can be a bus, aconnector, a telephone line interface, a wireless network interface, acellular network interface, a local area network interface, a broadbandcable interface, a telephone, a cellular phone, a cellular modem, atelephone data modem, a fax modem, a wireless transceiver, an Ethernetcard, a cable modem, a digital subscriber line interface, a bridge, ahub, a router, or other similar device.

[0032] Each processor 2200 can be a commercially availablegeneral-purpose microprocessor. In certain embodiments, the processorcan be an Application Specific Integrated Circuit (ASIC) or a FieldProgrammable Gate Array (FPGA) that has been designed to implement inits hardware and/or firmware at least a part of a method in accordancewith an embodiment of the present invention.

[0033] Memory 2300 can be coupled to processor 2200 and can comprise anydevice capable of storing analog or digital information, such as a harddisk, Random Access Memory (RAM), Read Only Memory (ROM), flash memory,a compact disk, a digital versatile disk (DVD), a magnetic tape, afloppy disk, and any combination thereof. Memory 2300 can also comprisea database, an archive, and/or any stored data and/or instructions. Forexample, memory 2300 can store instructions 2400 adapted to be executedby processor 2200 according to one or more activities of a method of thepresent invention.

[0034] Instructions 2400 can be embodied in software, which can take anyof numerous forms that are well known in the art. Instructions 2400 cancontrol operation of information device 2000 and/or one or more otherdevices, systems, or subsystems.

[0035] Input/output (I/O) device 2500 can be an audio and/or visualdevice, including, for example, a monitor, display, keyboard, keypad,touchpad, pointing device, microphone, speaker, video camera, camera,scanner, and/or printer, including a port to which an I/O device can beattached, connected, and/or coupled.

[0036]FIG. 3 is a block diagram of an exemplary embodiment of adifferential thermocouple 3000 of the present invention, which canrepresent differential thermocouple 1010 of FIG. 1. Differentialthermocouple 3000 can comprise two dissimilar metals joined by brazing,welding, soldering or mechanical fastening, for example. Typical metalsemployed include copper and constantan.

[0037] A first leg 3015 of copper wire, tube, rod or strip having aknown resistance is joined to a wire, tube, rod or strip of constantan3016 at a junction 3020. To the other end of the constantan wire, tube,rod or strip 3016 is a second leg 3018, formed of copper, identical inresistance to the leg 3015. The second leg 3018 is joined to theconstantan wire, tube, rod or strip 3016 at a junction 3022, with thejunctions 3020, 3022 being formed by tungsten inert gas welds, ofexample only. The legs 3015, 18 have terminal ends 3024, 3026,respectively. An electromotive force is developed across the terminalends 3024, 3026 of the legs 3015, 3018, in accordance with the equation:EMF=S_(AB) (T1−T2) where S_(AB) is the Seebeck coefficient for the legs3015, 3018 and the constantan wire, rod or strip 3016 and T1 and T2 arethe temperatures at the junctions 3020, 3022, respectively.

[0038]FIG. 4 is a flow diagram of an exemplary embodiment of a method4000 of the present invention. An analog transient signal, synchronizedwith the switching of the switches 1130, 1230 through the timing device1380, can be generated as an output of amplifier 1340. The analogtransient signal can be converted to a digital transient signal at A/Dconverter 1350. At activity 4100, the digital transient signal can bereceived at information device 1370.

[0039] At activity 4200, the digital transient signal then can beanalyzed to generate a total energy value E_(sig) pursuant to thefollowing algorithm: $\begin{matrix}\begin{matrix}{E_{sig} = \frac{\lim\limits_{n->30}{\sum\limits_{i = 1}^{n}\quad \left( {\int_{t_{1}}^{t_{2}}{{V}\quad {v}}} \right)}}{n}} \\{{{wherein}\quad n} = {{the}\quad {number}\quad {of}\quad {times}\quad {integration}\quad {is}\quad {{performed}.}}}\end{matrix} & \left( {{Equation}\quad 1} \right)\end{matrix}$

[0040] Essentially, a trigger point on the digital transient signal canbe obtained and counted for a fixed period of time to sum the totalenergy in the transient signal and generate a total energy sum.Integration of all amplitudes over the time period can produce a E_(sig)value representative of the energy present for the predetermine timeperiod in the transient signal. An average of integrated readings, e.g.seven reading, can be employed to improve accuracy.

[0041] At activity 4300, the value E_(sig) can employed to determine abalancing current I_(x) necessary to be applied to the balancing primarycoil 1220, in order to reduce E_(sig) to a zero value. Expressedmathematically,

I _(x) =lim _(E) _(sig) _(→0) f(E _(sig))  (Equation 2)

[0042] At activity 4400, information device 1370 can output, and/orsignal balancing current device 1250 to output, the balancing currentI_(x). At activity 4500, the balancing current I_(x) can be measured atinformation device 1370 and/or balancing current device 1250.

[0043]FIG. 5 is a flow diagram of an exemplary embodiment of a method5000 of the present invention. Method 5000 can include method 4000.

[0044] At activity 5100, the temperature T₁ at junction 1112 can beallowed to approach the temperature T₂ at junction 1114. At activity5200, using method 4000, a corresponding balancing current I₁ can bedetermined, output, and measured. At activity 5300, the temperature T₁at 1112 can be set to a value other than the temperature T₂ of 1114. Atactivity 5400, using method 4000, a corresponding balancing current I₂can be determined, output, and measured. At activity 5500, a currentdifferential I_(d)=|I₁−I₂| can be computed.

[0045] At activity 5600, a corresponding temperature differential and/orEMF, both of which are functions of I_(d), can be computed. At activity5700, the corresponding temperature differential and/or EMF can beoutput from information device 1370 to output device 1390.

[0046] To reduce interference, the timing device 1380 can be triggeredin phase with line current power supply, e.g. 60 cycle. For example, thetiming device can be triggered as the slope of the power supply waveapproaches zero. Pattern jitter does not necessarily have a significanteffect on the amplitude of the signal when the slope at the triggerpoint is near zero, i.e. at the peak or valley of the AC sine wave.

[0047] Utilization of an isothermal zone 1020 depicted in dashed linesin FIG. 1 can serve to reduce external thermal influences on thetransformer, resistors, and/or switches, and/or can substantially reduceadverse effects of noise. The components within zone 1020 can be placedinside a sealed housing at or below a pressure of one millitorr. Thecomponents can be coupled thermally, but not electrically, to atemperature controlled isothermal plate.

[0048] Elimination of junction thermo currents and condensation can beachieved, because the cold side of the isothermal plate can be placedwithin the housing.

[0049] The plate can be controlled to a fixed value temperature,dependent upon system requirements. Typically the temperature can bemaintained at between approximately 273° K to a theoretical value of 0°K, including every value therebetween.

[0050] The housing can be fabricated of a material with high thermalconductivity, e.g. one or more metals such as aluminum or copper. Thebottom surface of the housing can dissipate heat from the isothermalplate within the housing. The temperature of exterior surfaces of thehousing generally should not be low enough to permit condensation and anincrease in local humidity.

[0051] Thermoelectric modules controlled by an independent or integratedcontroller can be employed to cool the isothermal plate. Heat dischargedfrom the thermoelectric modules can be directed toward the housing tokeep the exterior of the housing above the dew point.

[0052] In lieu of thermoelectric modules, cryogenic fluids such asliquid nitrogen can be utilized to cool the isothermal zone within thechamber. Further, thermo piles and/or Peltier coolers can be embeddeddirectly into the isothermal plate.

[0053] Additionally, pure and/or inert dry gases can be employed withinthe chamber to enhance heat conduction without introducing air. Suchcontrol of the environment can reduce system instability attributed totemperature and/or humidity, e.g. can eliminate the effects of changesin magnetic permeability of the air within the transformer.

[0054]FIG. 6 is a circuit diagram of an exemplary embodiment of a system6000 of the present invention. System 6000 can resemble system 1000 ofFIG. 1. The second differential thermocouple 1210 of FIG. 1 can beeliminated and a balancing grounded resistor 1240 can be added, as shownin FIG. 6.

[0055] As also shown in FIG. 6, a first primary current supply device1150 and associated resistor 1160 can be connected to the first primarythermocouple circuit.

[0056] First primary current supply device 1150 can provide, via aresistor 1160, a current signal of a predetermined form, duration,amplitude, and/or direction through first differential thermocouple1110. For example, first primary current supply device 1150 can providea 200 milliamp current in a first direction through differentialthermocouple 1110 for a predetermined time, followed by a 200 milliampcurrent in the opposite direction for the same period of time.

[0057]FIG. 7 is a circuit diagram of an exemplary embodiment of a system7000 of the present invention. System 7000 can substantially resemblesystem 6000 of FIG. 6. The balancing current device 1170 and associatedresistor 1180 of FIG. 6 can be moved to the second primary circuit andrenumbered as balancing current device 1270 and associated resistor1280, as shown in FIG. 7, and can provide a current signal of apredetermined form, duration, amplitude, and/or direction through thesecond primary coil 1220.

[0058] An implementation of system 6000 and/or system 7000 can betheoretically viewed as being governed by certain equations, some ofwhich can be found in “Thermodynamics, An Introduction to the PhysicalTheories of Equilibrium Themostatics and Irreversible Thermodynamics”,by Herbert B. Callen, published by John Wiley & Sons, Inc., New York,May 1961, which is incorporated herein by reference in its entirety.

[0059] Other theoretical views of various embodiments are possible. Forexample, consider a differential thermocouple (e.g., 1110) composed oftwo thermoelement materials, A and B, with absolute Seebeck coefficientsof SA and SB, and a relative Seebeck coefficient of S. Characterizationof the voltage-current characteristic of this thermocouple can showsmall non-linearities. The voltage across the thermocouple can be givenby:

E=E ₀ +R _(e) I+QR _(th) S  (Equation 3)

[0060] where E₀ is the Seebeck voltage for the zero current case, Re isthe electrical resistance of the thermocouple loop, I is the current, Qis the heat transferred by the Peltier effect away from the A/B junctionand into the B/A junction, R_(th) is the thermal resistance of thejunctions with their environment, and S is the Seebeck coefficient.

[0061] The second term on the right side of Equation 1 can be expandedto explicitly show the effects of Joule heating:

R _(e) I=(R ₀ +αΔT)I≈(R ₀ +αCI ²)I  (Equation 4)

[0062] where α is the thermal coefficient of resistance of the wire, andC is a constant.

[0063] The third term on the right side of equation 1) can be simplifiedusing the relation between the Peltier coefficient Π and the Seebeckcoefficient, Π=S T:

Q=ΠI=STI  (Equation 5)

[0064] The result for the third term, divided by current is:

E(Peltier)/I=R _(th) S ² T  (Equation 6)

[0065] Thus, the ratio E(Peltier)/I can be proportional to absolutetemperature, with a mathematical proportionality constant of R_(th)S².

[0066] The R_(e) term can be separated from the Peltier term in a seriesof measurements. R₀ can be independent of the measurement speed, whereasthe Joule heating and Peltier effects can require a temperaturenon-uniformity to develop over several milliseconds to seconds.Furthermore, the Joule heating can enter as a higher power of currentcompared to the Peltier effect. Thus, the three terms can bedistinguished by establishing the current-voltage characteristic of thedifferential thermocouple, for example, at several frequencies.

[0067] The thermal resistance of the junction to its environment can bedependent on the following properties: thermal conductivity of thethermocouple elements; thermal conductivity of any sheath materialssurrounding the elements, and/or thermal transport properties of theenvironment in which the thermocouple is immersed. In general, each ofthese properties will be temperature dependent.

[0068] The Seebeck coefficient can be temperature dependent as well. Forsome combinations (type B, for example), the sign of S can even change.

[0069] The prefactor (R_(th)S²) consequently can depend on the choice ofthermocouple type, and for any thermocouple type the value of theprefactor can depend on temperature. A measurement of E(Peltier)/I alonedoes not necessarily give a direct measure of absolute temperature. Ameasurement of the prefactor, or via a separate combination ofmeasurements, the components of the prefactor, can provide a method fordirectly measuring absolute thermodynamic temperature.

[0070]FIG. 8 is a set of inter-linked timing diagrams of an exemplaryembodiment of a method 8000 of the present invention that can providesuch a direct measure of absolute thermodynamic temperature. Timingdiagram 8100 depicts a State 1, where I≠0, and timing diagram 8200depicts a State 2, where I=0. As a general note, in certain alternativeembodiments, openings and/or closings of one or more switches and/orcircuits described herein can be reversed.

[0071] For State 1, with the temperature differential of thethermocouple junctions, T₂−T₁, approximately equal to 0, using method4000, a balancing current I_(x) can be iteratively determined thatdrives E_(sig) to zero or nearly zero, as limited by the sensitivity ofthe measuring instruments. A State 1 EMF corresponding to I_(x) can thenbe computed.

[0072] For State 2, referring to FIG. 6, the circuit between firstprimary coil 1120 and ground can be opened via switch 1130 so thatcurrent does not flow through coil 1120. First primary current source1150 can supply a “push” current I₁ through thermocouple 1110 in a firstdirection for a time t1, followed by “pull” current 12 through 1110 in asecond, opposite direction for a time t2, where I₁=I₂, and t₁=t₂. Then,the circuit between first primary coil 1120 and ground can be completedvia switch 1130 so that current does flow through and charges coil 1120for a time t3=t2=t1.

[0073] Next, the circuit between first primary coil 1120 and ground canbe opened via switch 1130 so that a transient signal is generated fromsecondary coil 1320. Using method 4000, a balancing current I_(y) can beiteratively determined that drives E_(sig) to zero or nearly zero, aslimited by the sensitivity of the measuring instruments. A State 2 EMFcorresponding to I_(y) can then be computed, and a differential EMF==ΔEMF=|(State 1 EMF−State 2 EMF)| can be computed. Also, a time intervalt₄ can be measured from the time the final I_(x) is determined to thetime the final I_(y) is determined.

[0074] Next, first primary current source 1150 can be set to supply nocurrent, i.e., I₁=I₂=0, and the switch can be closed to allow aninternal current of the thermocouple can be allowed to flow throughfirst primary coil 1120 to ground. The switch can be opened to generatea transient signal from the secondary coil.

[0075] Then, the process can return to State 1, and a time interval t5can be measured from the time the final I_(y) is determined to the timethe final I_(x) is determined.

[0076] The process can iteratively continue through State 1 and State 2until Δ EMF converges on a constant and/or the change in Δ EMF convergeson 0. The constant value to which Δ EMF converges represents thetemperature change in the thermocouple due to Peltier effects. Method8000 can be repeated as many times as needed to improve the accuracy ofthe A EMF determination. Time intervals t₁, t₂, t₃, t₄, and/or t₅,and/or the work cycle employed in method 8000 can be utilized to computeabsolute temperature. A theoretical basis for these computations can befound in, for example, the explanation provided by Callen (referencedsupra).

[0077] In addition, method 8000 can include determining a Peltiercoefficient and/or Peltier effect of the differential thermocoupleindependently of EMF. Method 8000 also can include determining an EMFtime rate of change due to the Peltier work cycle, thermophysicalproperties (e.g., materials of construction, specific heat, thermalconductivity, heat capacity, etc.) of the sensor and/or its surroundingenvironment, and/or a degree of thermal coupling between the sensor andthe surrounding environment (e.g., how well the sensor is thermallyconnected to environment and/or how well heat is exchanged between thesensor and the environment).

[0078] From measurement of the Peltier effect at various temperatures,the thermodynamic temperature scale can be realized. The resolution ofthe absolute temperature measurements that provide this scale can befrom approximately 100 mK to approximately 10 mK to approximately 1 mKto approximately 0.1 mK, and every value therebetween.

[0079] Various embodiments can allow the Peltier work cycle to berelated directly to true thermodynamic temperature or absolutetemperature. Because a practical temperature scale is not necessarilyrequired, this advancement can allow improvements in many systems ofmeasurement that depend on temperature measurements. Various embodimentspresent the possibility, minus losses, of measuring heat directly interms of a work cycle.

[0080] There are numerous potential applications for various embodimentsof the present invention. For example:

[0081] Fundamental physical constants can be improved. For example, theaccuracy of Boltzman's constant (k) can possibly be improved byrealizing the thermodynamic temperature term of the fundamental gas law.

[0082] A sensor's thermal coupling to its environment can be assessed.

[0083] The practical temperature scale can be improved. For example, thedistance between the thermal energy states of the triple point of waterand the triple point of Gallium, respectively, can be determined withgreater accuracy and/or precision.

[0084] Thermal properties of materials, such as for example, thermalconductivity, specific heat, etc. can be measured more accurately and/orprecisely.

[0085] A better understanding of the conversion of heat to energy,and/or energy to heat, can be obtained by measurement.

[0086] Thermocouples can be used for accurate measurements without theneed for recalibration as the long term EMF shifts occurring during usewill not necessarily effect the work cycle measurement.

[0087] The system can measure the work cycle of all thermocouple typeswithout specifying the type.

[0088] Although the invention has been described with reference tospecific embodiments thereof, it will be understood that numerousvariations, modifications and additional embodiments are possible, andaccordingly, all such variations, modifications, and embodiments are tobe regarded as being within the spirit and scope of the invention. Also,references specifically identified and discussed herein are incorporatedby reference as if fully set forth herein. Accordingly, the drawings anddescriptions are to be regarded as illustrative in nature, and not asrestrictive.

What is claimed is:
 1. A method, comprising: providing an input signalfrom a first differential temperature sensor to a first primary coil ofa transformer, detecting a transient signal from a secondary coil of thetransformer, said transient signal arising upon a halting of the inputsignal.
 2. The method of claim 1, further comprising surrounding atleast a portion of the first differential temperature sensor with anisothermal zone.
 3. The method of claim 1, further comprisingsurrounding a cold end portion of the first differential temperaturesensor with an isothermal zone.
 4. The system of claim 1, furthercomprising thermally connecting an isothermal plate to the transformer.5. The system of claim 1, further comprising thermally connecting anisothermal plate to a resistor connected to the transformer.
 6. Thesystem of claim 1, further comprising thermally connecting an isothermalplate to a transistor connected to the transformer.
 7. The system ofclaim 1, further creating a stable isothermal zone for the transformerand a connection to a cold end portion of the first differentialtemperature sensor.
 8. The method of claim 1, further comprisingexposing the first differential temperature sensor to a differentialtemperature.
 9. The method of claim 1, further comprising exposing a hotend of the first differential temperature sensor to a differentialtemperature.
 10. The method of claim 1, further comprising modulating aDC signal from the first differential temperature sensor to form theinput signal.
 11. The method of claim 1, further comprising modulating aDC signal from the first differential temperature sensor to form theinput signal, the input signal resembling a square wave.
 12. The methodof claim 1, further comprising modulating a DC signal from the firstdifferential temperature sensor to form the input signal, the inputsignal resembling a square wave having a duty cycle.
 13. The method ofclaim 1, further comprising modulating a DC signal from the firstdifferential temperature sensor to form the input signal, the inputsignal resembling a square wave having an uneven duty cycle.
 14. Themethod of claim 1, further comprising modulating a DC signal from thefirst differential temperature sensor to form the input signal, theinput signal resembling a square wave having a phase matched to an ACpower source coupled to a modulator that causes said modulating.
 15. Themethod of claim 1, further comprising attaching a second differentialtemperature sensor to a second primary coil of the transformer.
 16. Themethod of claim 1, further comprising attaching a second differentialtemperature sensor to a second primary coil of the transformer andproviding a balancing signal to the second input coil.
 17. The method ofclaim 1, further comprising balancing the input signal with a balancingsignal.
 18. The method of claim 1, further comprising correlating anaverage total energy present in the transient signal to a zerotemperature differential sensed by the differential temperature sensor.19. The method of claim 1, further comprising measuring energy in thetransient signal.
 20. The method of claim 1, further comprisingmeasuring a form of the transient signal.
 21. The method of claim 1,further comprising determining total energy in the transient signal overa fixed period of time.
 22. The method of claim 1, further comprisingproviding a current to a second primary coil of the transformer to causean energy present in the transient signal to equal a zero-state energypresent in a zero-state transient signal produced when a zerotemperature differential is sensed by the differential temperaturesensor.
 23. The method of claim 1, further comprising providing acurrent to a second primary coil of the transformer to cause an energypresent in the transient signal to equal a zero-state energy present ina zero-state transient signal produced when a zero temperaturedifferential is sensed by the differential temperature sensor, andcorrelating the provided current to a temperature differential sensed bythe differential temperature sensor.
 24. The method of claim 1, furthercomprising applying a current to the temperature differential sensor.25. The method of claim 1, further comprising applying a first currentto the temperature differential sensor in a first direction.
 26. Themethod of claim 1, further comprising applying a first current to thetemperature differential sensor in a first direction, and applying asecond current to the temperature differential sensor in a second,opposite direction.
 27. The method of claim 1, further comprisingapplying a first current to the temperature differential sensor for afirst time period, and applying a second current to the temperaturedifferential sensor in a direction opposite to that of the first currentfor a second time period.
 28. The method of claim 1, further comprisingapplying a first current to the temperature differential sensor for afirst time period, and applying a second current to the temperaturedifferential sensor in a direction opposite to that of the first currentfor a second time period, said second current equal in magnitude to saidfirst current.
 29. The method of claim 1, further comprising applying afirst current to the temperature differential sensor for a first timeperiod, and applying a second current to the temperature differentialsensor in a direction opposite that of the first current for a secondtime period, said first time period equal to said second time period.30. The method of claim 1, further comprising applying a first currentto the temperature differential sensor for a first time period, andapplying a second current to the temperature differential sensor in adirection opposite that of the first current for a second time period,the second current equal to the first current, and correlating a Peltiereffect associated with the temperature differential sensor.
 31. Themethod of claim 1, further comprising measuring a Peltier effectassociated with the differential temperature sensor.
 32. The method ofclaim 1, further comprising quantifying a Peltier effect associated withthe differential temperature sensor.
 33. The method of claim 1, furthercomprising determining a Peltier effect associated with the differentialtemperature sensor.
 34. The method of claim 1, further comprisingcompensating for a Peltier effect associated with the differentialtemperature sensor.
 35. The method of claim 1, further comprisingdetermining a temperature differential sensed by the differentialtemperature sensor.
 36. The method of claim 1, further comprisingdetermining a temperature differential sensed by the differentialtemperature sensor to within 0.001 K.
 37. The method of claim 1, furthercomprising determining a temperature differential sensed by thedifferential temperature sensor to within 0.0001 K.
 38. The method ofclaim 1, wherein the differential temperature sensor is a differentialthermocouple.
 39. The method of claim 1, wherein the differentialtemperature sensor comprises one or more p-n semiconductor elements. 40.A method, comprising: providing an input signal from a current-producingtransducer to a primary of a transformer, detecting a transient signalfrom a secondary of the transformer, said transient signal arising upona halting of the input signal.
 41. A method, comprising: detecting atransient signal from a secondary coil of a transformer, the transientsignal arising upon an interruption of an input signal from acurrent-producing transducer provided to a first primary coil of thetransformer, providing a current to the second primary coil of thetransformer to cause an energy present in the transient signal to equala reference energy present in a reference transient signal produced bythe secondary coil of the transformer when no temperature differentialis sensed by the current-producing transducer.
 42. The method of claim41, further comprising detecting a reference transient signal from thesecondary coil of the transformer, the reference transient signalarising upon an interruption of a reference input signal from thecurrent-producing transducer provided to the first primary coil of thetransformer when no temperature differential is sensed by thecurrent-producing transducer.
 43. The method of claim 41, furthercomprising applying a first current to the current-producing transducerto create a first Peltier effect, and applying a second current to thecurrent-producing transducer in a direction opposite that of the firstcurrent to create an equal and opposite second Peltier effect.
 44. Themethod of claim 41, further comprising applying a first current to thecurrent-producing transducer to create a first Peltier heat flow, andapplying a second current to the current-producing transducer in adirection opposite that of the first current to create a second Peltierheat flow equal and opposite to the first Peltier heat flow.
 45. Themethod of claim 41, further comprising applying a first current to thecurrent-producing transducer for a first time period, and applying asecond current to the current-producing transducer in a directionopposite that of the first current for a second time period, the secondtime period equal to the first time period, and determining a net EMFcorresponding to a combined effect of the first current and the secondcurrent.
 46. A system, comprising a first differential thermocouplesensor electrically coupled to a first modulator having a duty cycle, anoutput of said first modulator electrically coupled to a first primarycoil of a transformer, and a second differential thermocouple sensorelectrically coupled to a second modulator having a duty cycle, saidsecond modulator electrically coupled to a second primary coil of saidtransformer, said first primary coil balanced with said second primarycoil, a secondary coil of said transformer electrically coupled to saidfirst a processor adapted to detect a transient output of said secondarycoil of said transformer and filter a steady-state output of saidsecondary coil of said transformer.
 47. The system of claim 46, furthercomprising a timed switch controlling an output of said first modulator.48. The system of claim 46, further comprising a timing generatorcontrolling an output of said first modulator.
 49. The system of claim46, further comprising an amplifier electrically coupled between saidsecondary coil of said transformer and said processor.
 50. The system ofclaim 46, further comprising an amplifier electrically coupled betweensaid secondary coil of said transformer and said processor.
 51. Thesystem of claim 46, further comprising an amplifier having apredetermined gain, said amplifier electrically coupled between saidsecondary coil of said transformer and said processor.
 52. The system ofclaim 46, further comprising an analog-to-digital converter electricallycoupled between said secondary coil of said transformer and saidprocessor.
 53. The system of claim 46, further comprising a nullingfeedback loop from said processor to said second primary coil of saidtransformer, said nulling feedback loop comprising a current registeringdevice.
 54. The system of claim 46, further comprising a chambercontaining said transformer, said chamber maintaining a pressure of lessthan approximately 2 millitorr.
 55. The system of claim 46, furthercomprising a chamber containing said transformer and an inert gas. 56.The system of claim 46, further comprising a chamber containing saidtransformer and a dry gas.
 57. The system of claim 46, furthercomprising a chamber containing said transformer and a dry mixture ofgases.
 58. The system of claim 46, further comprising an isothermalplate thermally connected to said transformer.
 59. A system, comprisinga differential temperature sensor electrically coupled to a modulatorhaving a duty cycle, said modulator electrically coupled to a primarycoil of a transformer, a secondary coil of said transformer electricallycoupled to a processor adapted to detect a transient output of saidsecondary coil of said transformer.
 60. A system, comprising: a frontend circuit comprising a current-producing transducer electricallycoupled to a modulator, said modulator electrically coupled to a primarycoil of a transformer, a back end circuit comprising a secondary coil ofsaid transformer coupled to a processor, a current source electricallycoupled to said processor and to said secondary coil of saidtransformer, a timed trigger electrically coupled to said front endassembly.
 61. A system comprising: a current-producing transducerelectrically coupled to a primary coil of a transformer; a timed triggerelectrically coupled to said transformer, a secondary coil of saidtransformer coupled to a processor.
 62. A first transient signal from anoutput of a secondary coil of a transformer, said first transient signalarising from halting an input current applied to an input of a primarycoil of the transformer, said input current comprising a modulated DCcurrent, said DC current output from a current-producing transducer. 63.A first transient signal from an output of a secondary coil of atransformer, said first transient signal arising from halting an inputcurrent applied to an input of a primary coil of the transformer, saidinput current comprising a modulated DC current, said DC current outputfrom a differential temperature sensor.
 64. A first transient signalfrom an output of a secondary coil of a transformer, said firsttransient signal arising from halting an input current applied to aninput of a first primary coil of the transformer, said input currentcomprising a modulated DC current, said DC current output from acurrent-producing transducer, a reference current applied to a secondprimary coil of the transformer corresponding to a reference transientsignal arising from halting a reference input current applied to theinput of the first primary coil of the transformer, the reference inputcurrent related to a reference DC current output from thecurrent-producing transducer when the current-producing transducer isexposed to a zero differential temperature.
 65. A method, comprising:determining a zero-current EMF across a differential thermocouple;determining a non-zero-current EMF across the differential thermocouple;and determining a differential EMF across the differential thermocouple.66. The method of claim 65, further comprising determining an absolutetemperature from the differential EMF.
 67. The method of claim 65,further comprising determining an absolute thermodynamic temperaturefrom the differential EMF.
 68. The method of claim 65, furthercomprising determining a Peltier coefficient of the differentialthermocouple.
 69. The method of claim 65, further comprising determininga Peltier coefficient of the differential thermocouple independently ofEMF.
 70. The method of claim 65, further comprising determining an EMFtime rate of change due to a Peltier work cycle, thermophysicalproperties (e.g., specific heat, thermal conductivity, heat capacity,etc. of materials of consturction of thermocouple and/or environment) ofthe sensor and a surrounding environment, and a degree of thermalcoupling (how well sensor is thermally connected to environment (i.e.,how well heat is exchanged between sensor and environment) between thesensor and the surrounding environment.
 71. The method of claim 65,wherein said determining a zero-current EMF further comprises flowing afirst current in a first direction through the differential thermocoupleand flowing a second current in a second direction through thedifferential thermocouple, the first current equal in magnitude to thesecond current, the first direction opposite the second direction. 72.The method of claim 65, wherein said measuring a zero-current EMFfurther comprises flowing a first current in a first direction throughthe differential thermocouple; flowing a second current in a seconddirection through the differential thermocouple the first current equalin magnitude to the second current, the first direction opposite thesecond direction; and halting flow of the first and second currents. 73.The method of claim 65, wherein said measuring a zero-current EMFfurther comprises flowing a first current in a first direction throughthe differential thermocouple; flowing a second current in a seconddirection through the differential thermocouple the first current equalin magnitude to the second current, the first direction opposite thesecond direction; and allowing an internal current to flow through thedifferential thermocouple and primary coil of a transfomer.
 74. Themethod of claim 65, wherein said measuring a zero-current EMF furthercomprises flowing a first current in a first direction through thedifferential thermocouple; flowing a second current in a seconddirection through the differential thermocouple the first current equalin magnitude to the second current, the first direction opposite thesecond direction; and causing a transient signal to propagate from asecondary coil of a transformer.